Electronics assembly

ABSTRACT

An electronics assembly comprises a frame ( 1 ) that contains a motherboard ( 8 ) and a plurality of daughterboards ( 10 ). The frame has  
     (i) an opening opposite the motherboard to allow insertion of the daughterboards into the frame or removal of the daughterboards from the frame;  
     (ii) an injector/ejector mechanism ( 16, 18 ) for each daughterboard that is located on the daughterboard or the frame; and  
     (iii) a flange ( 28 ) that extends therealong at or adjacent to the opening and on which the injector/ejector mechanism of each daughterboard is attached or engages at different locations along the length thereof.  
     The flange ( 28 ) is divided into separate sections ( 30 ) that correspond to the different locations to allow the flange to flex at any location therealong during insertion of a daughterboard without the flexing affecting the position of any adjacent location of the flange with respect to the motherboard.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to electronics assemblies, and isprimarily concerned with racked assemblies. Many such assemblies will belocated in racks for housing in for example nineteen inch cabinets, orother size cabinets such as twenty three inch or metric cabinets. Theassemblies may for instance be employed as servers for a number ofsystems, for example in local area networks (LANS), wide area networks(WANs), telecommunications systems or other operations such as databasemanagement or as internet servers.

[0002] Such an assembly will typically comprise a supporting frame thathouses a motherboard or backplane and a number of daughterboards ormodule cards that extend in planes generally perpendicular to the planeof the motherboard and which are connected to the motherboard byconnectors, e.g. high density connectors, so that the daughterboards cansimply be introduced into the frame through an opening therein oppositethe motherboard, located on guides and pushed toward the motherboard inorder to connect them to it.

[0003] Each daughterboard usually requires multiple electricalconnections which are generally provided by two-part multi-pinelectrical connectors, one part of which is located at the rear of thedaughterboard and the other part provided on the motherboard.

[0004] In order to engage the daughterboard and the motherboardconnectors properly during insertion, and to aid removal of thedaughterboards, it is common to employ injector/ejector mechanisms. Aninjector/ejector mechanism is operated by a user and is intended toensure an appropriate even force to be applied to the electricalconnectors between the motherboard and the daughterboards duringinsertion of the daughterboard, to lock the daughterboard in placeduring operation of the system and to aid disconnection of theelectrical connectors during removal of the daughterboard. The mostcommon form of injector/ejector mechanism comprises a lever arm that canbe pivotally located on a flange on the frame at or adjacent to theopening or, more usually, located on the daughterboard and engage theflange, in order to provide a mechanical advantage during connection ordisconnection.

[0005] One problem that has been encountered with such assemblies,however, is ensuring correct electrical connection between thedaughterboards and the motherboard due to dimensional tolerances in thedaughterboards and other parts of the assembly. The daughterboards may,for example, have typical dimensions in the region of 500 mm in theinsertion and removal direction whereas the connectors may have a lengthof travel between initial contact of the pins and complete mating of theconnectors, or so-called “wipe”, as low as 0.5 to 0.8 mm, with theresult that because of tolerances in the length of the daughterboards,some connectors may be overstressed while other connectors may not forma good connection. This problem is particularly severe if daughterboardstoward the end of an array are relatively long and cause the flange tobow, while daughterboards at the centre of the array are relativelyshort.

[0006] This problem may be resolved by providing a flexible coupling inthe injector/ejector mechanism to allow relative movement of adaughterboard away from the motherboard while applying a biasing forcetoward the motherboard. Although such a system is perfectly adequate inresolving the problem, it requires discrete components to beincorporated in each injector/ejector mechanism and is thereforerelatively expensive to implement.

SUMMARY OF THE INVENTION

[0007] According to one aspect, the present invention provides anelectronics assembly which comprises a frame that contains a motherboardand a plurality of daughterboards that extend in a plane generallyperpendicular to the plane of the motherboard and are connected to themotherboard by means of connectors, the frame having:

[0008] (i) an opening opposite the motherboard to allow insertion of thedaughterboards into the frame or removal of the daughterboards from theframe in a direction normal to the plane of the motherboard;

[0009] (ii) an injector/ejector mechanism for each daughterboard that islocated on the daughterboard or the frame and engages the frame or thedaughterboard respectively in a region adjacent to the opening; and

[0010] (iii) a flange that extends therealong at or adjacent to theopening and on which the injector/ejector mechanism of eachdaughterboard is attached or engages at different locations along thelength thereof,

[0011] wherein the flange is divided into separate sections thatcorrespond to the different locations to allow the flange to flex at anylocation therealong during insertion of a daughterboard without theflexing affecting the position of any adjacent location of the flangewith respect to the motherboard.

[0012] According to another aspect, the present invention provides aframe for an electronics assembly which comprises a location in which aplanar motherboard can be received and a plurality of guides that extendin a direction generally normal to the plane of the motherboard when itis received in the frame in order to enable a plurality ofdaughterboards to be located in the frame in engagement with themotherboard, the frame having:

[0013] (i) an opening opposite the location for the motherboard to allowinsertion of the daughterboards into the frame or removal of thedaughterboards from the frame; and

[0014] (ii) a flange that extends therealong at or adjacent to theopening and along which an injector/ejector mechanism for eachdaughterboard is attached or can engage at different locations along thelength thereof;

[0015] wherein the flange is divided into separate sections thatcorrespond to the different locations to allow the flange to flex at anylocation therealong during insertion of a daughterboard without theflexing affecting the position of any adjacent location of the flangewith respect to the location of the motherboard.

[0016] The assembly and frame according to the invention enabledaughterboards of different dimensional tolerances to be accommodatedwithin the frame and biased into engagement with the motherboard in aparticularly inexpensive manner since no discrete biasing components arerequired.

[0017] The injector/ejector mechanism for each daughterboard may, forexample, comprise a lever arm that is located on the daughterboard andengages the flange or is located on the flange and engages thedaughterboard. Usually the injector/ejector mechanism will be in theform of a lever arm that is pivotally attached to the daughterboard andhas a relatively short (i.e. in relation to the arm) projection thatengages the flange and moves the daughterboard toward the motherboardwhen the lever arm is moved toward the front edge of the daughterboardso that it provides a degree of mechanical advantage during insertion ofthe daughterboard.

[0018] Although only one injector/ejector mechanism has been referred toin respect of each daughterboard, the assembly will usually have twosuch mechanisms for each daughterboard, one mechanism being located ateach end of the front edge of the daughterboard or on each side of theopening and the frame will accordingly have a flange on each side of theopening.

[0019] The frame will normally have a strengthening member that extendsalong a side thereof, and usually along both sides thereof, in theregion of the opening in order to provide the frame with rigidity in theplane of the daughterboards. That is to say, the or each strengtheningmember will extend along the or each side of the opening in a directionnormal to the plane of the daughterboards in order to reduce the degreeto which the or each side of the strengthening member bows out in adirection in the plane of the daughterboards. Typically thestrengthening member will extend parallel to and adjacent to the flange.It may be formed separately from the flange, for example where theflange is formed by folding a front edge portion of the material formingthe sides of the frame, and attached to the sides of the frame in anyappropriate manner. Alternatively, if the strengthening member and theflange are in close proximity to one another, it may be convenient toform them both from the same element. For example, they may both beformed together as a beam having a substantially “C” or “S”-shapedcross-section where one side web of the beam constitutes the flange anda web forming the other side of the beam constitutes the strengtheningmember.

[0020] Such a form of beam is novel per se and so, according to anotheraspect, the invention comprises an abutment beam for engaging aplurality of injector levers for urging daughterboards onto finalengagement with a motherboard in an electronic circuit housed in acasing, the abutment beam having a first web attachable to the housingand a second web comprising a plurality of separated locations forengaging the injector levers, each location of the second web beingindependently flexible relative to the first web.

[0021] Whether the flange and the strengthening member are formed asseparate parts or are formed together, the strengthening member isadvantageously arranged on the side of the flange between the flange andthe motherboard. Such an arrangement enables the injector/ejectormechanism, for example the projection of the lever arm, to bear on theflange when the daughterboard is inserted into the frame and theconnectors of the daughterboard and the motherboard are mated, and alsowhen the daughterboards are retained in position in engagement with themotherboard during operation. In this way, resilient deformation of theseparate sections of the flange will exert a bias force on thedaughterboards to maintain the connectors in engagement whileaccommodating any difference in dimensions of the daughterboards. On theother hand, no such resilient deformation is required when thedaughterboards are removed and so the injector/ejector mechanism canbear on the strength member.

[0022] The flange may be divided into the separate sections by formingdiscontinuities such as slots or slits therein at the appropriatepositions, for example by sawing or shearing. There is a relativelylarge degree of freedom in the depth of the slots, although to increasethe distance over which the different sections of the flange may move,the depth of the slots may be as great as the flange width so that a “C”section beam would be cut into a corner of its cross-section. Indeed,the slot depth may be greater where the beam is attached to a side wallof the frame since the wall itself will provide rigidity in thedirection of insertion or removal of the daughterboards. There is,however, not usually any advantage in increasing the depth of the slotsor slits beyond the width of the flange, and where no side wall ispresent the strength of any strengthening member in the direction ofinsertion or removal will be reduced.

[0023] Other forms of assembly and frame may be employed within thescope of the invention. More than one flange and/or strengthening membermay be arranged on each side of the opening, for example, or the flangeand/or the strengthening member may be formed separately as beams havingan “L”-shaped cross-section. In addition, instead of a lever arm havinga single projection that bears on different surfaces (the flange and thestrengthening member) for insertion and removal of the daughterboards,two projections may be provided on the lever arm that bear on oppositesides of the flange so that one projection is employed for insertion andthe other is employed for removal.

[0024] It is not necessary for the flange and/or the strengtheningmember to be formed from the same material as each other or as the sidewall of the frame but may be formed, for example, from plastics materialthereby allowing a different degree of flexibility or rigidity.

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Embodiments of the present invention will now be described indetail with reference to the accompanying drawings, in whichcorresponding parts are given like reference numbers. In the drawings:

[0026]FIG. 1 is a side view of a daughterboard in a conventionalelectronics assembly;

[0027]FIG. 2 is a view taken along the planes of the daughterboards ofthe assembly of FIG. 1;

[0028]FIG. 3 is a top plan view of an electronics assembly according toone embodiment of the present invention;

[0029]FIG. 4 is an enlarged view of a lever arm of the assembly shown inFIG. 3;

[0030]FIG. 5 is a view of part of the assembly of FIG. 3 taken along theplanes of the daughterboards;

[0031]FIG. 6 is an isometric view of part of another embodiment of thepresent invention;

[0032]FIG. 7 is an isometric view of a modification of the embodimentshown in FIG. 6; and

[0033]FIG. 8 is a section through part of another embodiment of thepresent invention.

DESCRIPTION OF PARTICULAR EMBODIMENTS

[0034] Referring now to the drawings, in which like reference numeralsare used to designate corresponding elements, FIG. 1 shows part of aconventional electronics assembly in which a frame 1 forming part of thechassis of the assembly has two side walls 2 and 4 and a rear wall 6that houses a pcb forming a backplane or motherboard 8. Opposite themotherboard 8 is an opening through which a daughterboard 10 can beinserted into the frame or removed therefrom. The daughterboard can beinserted into the frame and slid along guides (not shown) toward themotherboard until a multi-contact connector 12 on the daughterboardmates with a corresponding multi-contact connector 14 on themotherboard.

[0035] In order to facilitate mating of the connectors 12 and 14 duringinsertion of the daughterboard, and also disconnection of the connectorsduring removal of the daughterboard, two injector/ejector arrangementsare provided in the form of a lever arm 16 that is located on each sideof the front edge 18 of the daughterboard and pivotal about a pivot axis20 thereon. The lever arm 16 has a short projection 22 which is locatedbetween opposite sides of a beam 24 of substantially “C”-shapedcross-section when the daughterboard is, as shown, fully inserted intoframe and engaged with the motherboard connector 14. The daughterboardcan be moved out of engagement with the motherboard connector 14 bypulling the lever arms in the direction of arrows A which causes theprojection 22 to bear on the inner web or side arm 26 of the beam 24 andeject the daughterboard in the direction of arrows 13. The same actionsin reverse will cause the daughterboard to be received within the frame1 with the connectors 12 and 14 mated, and the projection 22 bearing onthe outer side arm or flange 28 in order to keep the daughterboards inplace.

[0036]FIG. 2 is a schematic view of the frame shown in FIG. 1 with threedaughterboards 10 a, 10 b and 10 c in place in which the twodaughterboards 10 a and 10 c toward the edges of the frame arerelatively large due to dimensional tolerances. This can cause the beam24 to bow outwards (the degree of bowing is grossly exaggerated for thesake of clarity) and cause the distance X between the beam and themotherboard to be increased. If the middle daughterboard 10 b is itselfrelatively short this can cause inadequate mating of the connectors 12 band 14 b. In addition, the outer daughterboards are subject to stress.

[0037]FIG. 3 shows one form of assembly according to the invention seenthrough the opening for insertion of the daughterboards, while FIG. 4shows the engagement of one of the lever arms in greater detail and FIG.4 is a side view of part of the beam 24 with the daughterboards inplace. Three daughterboards 10 are inserted into their positions in theframe and three slots for the daughterboards are vacant, exposingconnectors 14 on the motherboard.

[0038] Instead of having a pair of continuously formed side arms, theinnermost side arm 26 of the beam 24 is continuous while the outermostside arm 28 that forms the flange against which the projections 22 ofthe lever arms 16 bear during insertion, is divided into separatesections 30 by means of slots 32 that extend up to the middle portion 34of the beam. By dividing this flange into separate sections 30, eachsection is capable of flexing to a different degree, as shown in FIG. 5,to accommodate differences in length of the various daughterboardswithout affecting the distance of the adjacent section 30 to themotherboard, so that all the daughterboards can be accommodated withoutbeing overstressed or forming a poor electrical connection to themotherboard. The innermost side arm 26 of the beam 24 is not dividedinto sections so that it will still provide strengthening and rigidityfor the side wall in the region of the front opening of the frame.Indeed, if the frame forms a card cage within a larger chassis, theremay not be any side wall of the frame. In addition, the innermost sidearm 26 that forms the strengthening member provides a surface againstwhich the projections 22 on the lever arms 16 can bear when thedaughterboard is ejected.

[0039] The beam may be formed from the same material as that of theframe and may be spot-welded, riveted or screwed in place, or it may beformed from a different material, for example plastics. In addition, thearrangement may be designed so that, even with a daughterboard 10 at theshortest end of the tolerance range, the daughterboard is held with abias against the motherboard connector.

[0040]FIG. 6 is an isometric view of part of a side wall of analternative form of assembly according to the invention. In thisembodiment the flange 28 is formed directly from the sheet that formsthe side wall 36 of the frame and slots 32 are cut therein as far as theplane of the side wall in order to divide it into sections 30. Aseparate strengthening member 26 in the form of a beam of “L”-shapedcross-section is attached to the side wall 36 of the frame. If desired,the strengthening member could be formed in a side wall 36 of the frameby pressing the sheet from which the side wall is formed to form anoutwardly oriented ledge as shown in FIG. 7.

[0041]FIG. 8 shows a further form of assembly according to the inventionin which the flange 28 on which the projection 22 of the lever arm 16bears forms part of a beam 24 of substantially “S”-shaped cross-section.The outermost part of the beam 24 against which the projections 22 ofthe lever arms bear during insertion of the daughterboards and duringretention thereof within the frame is divided into sections for eachdaughterboard in the same manner as shown in FIGS. 3 to 6, while theremaining four surfaces 38, 40, 42 and 44 are continuous and providerigidity to the structure. This design of beam will exhibit stiffnessboth in the direction of insertion and removal of the daughterboards(vertically as shown in FIG. 7) and also in the plane of thedaughterboards (horizontally as shown in FIG. 7) and may be employed forexample where the frame forms a card cage within a larger structure andso no side wall of the frame may be present on either or both sidesthereof.

[0042] It would be possible, in the arrangement as shown in FIG. 8, forthe slots or slits in the beam 24 to extend further and to divide atleast part of the surface 38 into sections, thereby allowing a greaterdegree of flexing of the sections 30 although the overall stiffness ofthe beam would be reduced to some extent.

[0043] The scope of the present disclosure includes any novel feature orcombination of features disclosed therein either explicitly orimplicitly or any generalisation thereof irrespective of whether or notit relates to the claimed invention or mitigates any or all of theproblems addressed by the present invention. The applicant hereby givesnotice that new claims can be formulated to such features during theprosecution of this application or of any such further applicationderived therefrom. In particular, with reference to the appended claims,features from dependent claims can be combined with those of theindependent claims and features from respective independent claims canbe combined in any appropriate manner and not merely in the specificcombinations enumerated in the claims.

1. An electronics assembly which comprises a frame that contains amotherboard and a plurality of daughterboards that extend in a planegenerally perpendicular to the plane of the motherboard and areconnected to the motherboard by means of connectors, the frame having:(i) an opening opposite the motherboard to allow insertion of thedaughterboards into the frame or removal of the daughterboards from theframe in a direction normal to the plane of the motherboard; (ii) aninjector/ejector mechanism for each daughterboard that is located on thedaughterboard or the frame and engages the frame or the daughterboardrespectively in a region adjacent to the opening; and (iii) a flangethat extends therealong at or adjacent to the opening and on which theinjector/ejector mechanism of each daughterboard is attached or engagesat different locations along the length thereof, wherein the flange isdivided into separate sections that correspond to the differentlocations to allow the flange to flex at any location therealong duringinsertion of a daughterboard without the flexing affecting the positionof any adjacent location of the flange with respect to the motherboard.2. An assembly as claimed in claim 1, wherein the injector/ejectormechanism for the daughterboard comprises a lever arm that is located onthe daughterboard and engages the flange or is located on the flange andengages the daughterboard.
 3. An assembly as claimed in claim 2, whereinthe lever arm is located on the daughterboard and engages the flange. 4.An assembly as claimed in claim 1, wherein the frame has a strengtheningmember extending along a side thereof in the region of the opening inorder to provide the frame with rigidity in the plane of thedaughterboards.
 5. An assembly as claimed in claim 4, wherein thestrengthening member extends in parallel to, and adjacent to, theflange.
 6. An assembly as claimed in claim 4, wherein the strengtheningmember and the flange are formed from the same element.
 7. An assemblyas claimed in claim 6, wherein the strengthening member and the flangeare formed from a beam having a substantially “C” or “S” shapedcross-section.
 8. An assembly as claimed in claim 4, wherein thestrengthening member is arranged on the side of the flange, between theflange and the motherboard.
 9. An assembly as claimed in claim 8,wherein the injector/ejector mechanism bears on the flange when thedaughterboard is inserted into the frame and bears on the strengtheningmember when the daughterboard is removed.
 10. An assembly as claimed inclaim 1, wherein the flange is divided into the separate sections byslots or slits in the flange.
 11. A frame for an electronics assemblywhich comprises a location in which a planar motherboard can be receivedand a plurality of guides that extend in a direction generally normal tothe plane of the motherboard when it is received in the frame in orderto enable a plurality of daughterboards to be located in the frame inengagement with the motherboard, the frame having: (i) an openingopposite the location for the motherboard to allow insertion of thedaughterboards into the frame or removal of the daughterboards from theframe; and (ii) a flange that extends therealong at or adjacent to theopening and along which an injector/ejector mechanism for eachdaughterboard is attached or can engage at different locations along thelength thereof; wherein the flange is divided into separate sectionsthat correspond to the different locations to allow the flange to flexat any location therealong during insertion of a daughterboard withoutthe flexing affecting the position of any adjacent location of theflange with respect to the location of the motherboard.
 12. A frame asclaimed in claim 11, which has a strengthening member extending along aside thereof in the region of the opening in order to provide the framewith rigidity in the plane of the daughterboards.
 13. A frame as claimedin claim 12, wherein the strengthening member extends in parallel to,and adjacent to, the flange.
 14. A frame as claimed in claim 12, whereinthe strengthening member and the flange are formed from the sameelement.
 15. A frame as claimed in claim 14, wherein the strengtheningmember and the flange are formed from a beam having a substantially “C”or “S” shaped cross-section.
 16. A frame as claimed in claim 12, whereinthe strengthening member is arranged on the side of the flange, betweenthe flange and the motherboard.
 17. A frame as claimed in claim 11,wherein the breaks between different locations in the flange are formedby slots in the flange.
 18. An abutment beam for engaging a plurality ofinjector levers for urging daughterboards onto final engagement with amotherboard in an electronic circuit housed in a casing, the abutmentbeam having a first web attachable to the housing and a second webcomprising a plurality of separated locations for engaging the injectorlevers, each location of the second web being independently flexiblerelative to the first web.
 19. A beam as claimed in claim 18, whereinthe first and second webs are joined at respective longitudinal edges.20. A beam as claimed in claim 18, wherein the locations are separatedby slots or slits extending transversely of the second web.